Radiation sensitive silver-dye complexes



United States Patent RADIATION SENSITIVE SILVER-DYE COMPLEXES Paul B.Gilman, Charles A. Golie, and Jean E. Jones,

Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., acorporation of New Jersey No Drawing. Filed Nov. 16, 1964, Ser. No.411,594

Int. Cl. G03c 1/40 US. C]. 9663 40 Claims ABSTRACT OF THE DISCLOSURE Aradiation-sensitive composition which consists essentially of at leastone reaction product of silver and a spectral sensitizing dye which uponexposure to radiation forms active sites for physical development.Typical sensitlzing dyes include cyanines, merocyanines, oxonols,hemicyanines, hemioxonols, styryls and benzylidenes.

This invention concerns light sensitve photographic elementsparticularly those using a light sensitive coating containing a silvercomplex of a sensitizing dye.

Light sensitive coatings based on silver customarily used in photographyare based on silver halide compositions carried in water permeablecolloid layers. These silver halide emulsions are relatively expensiveto prepare due to the amount of silver used. Moreover, they produce aphotographic image which is limited in its resolving power due to thegraininess of the silver halide particles. In addition, the silverhalide emulsion normally requires chemical development including afixing step in which the undeveloped silver halide is removed. Thesilver halide salts do not absorb beyond about 500 m and must be dyedwith sensitizing dyes to produce sensitivity beyond that wavelength.

It is known that sensitizing dyes are effective with both slow and highspeed photographic emulsions. The same sensitizing dyes may confer greenor red sensitivity for both very slow emulsions or to the highest speedemulsions available. However, in the green or red region of the spectrumthe silver halide acts only as an acceptor of the response produced byexposure of the sensitizing dye. The limit of photographic sensitivitypossible is not limited by sensitizing dyes but by the substrate used toadsorb the dye.

The spectral sensitization of silver halide is based on the use of thesensitizing dye adsorbed to the silver halide surface. It is generallyaccepted that light energy absorbed by a mobile silver io nfrom thesilver halide lattice to manner that an electron appears in theconduction band of the silver halide, the electron is trapped andneutralized by a mobile silver ion from the silver halide lattice toform a speck of silver. The silver halide acts as a medium through whichthe dye passes its energy so that ultimately a speck of silver isformed.

Spectral sensitization of silver halide by addition thereto of thereaction product of a sensitizing dye and a soluble silver salt isknown. This reaction product, identified herein as the silver-dyecomplex, reacts with the silver halide to produce silver halide grainswith the dye adsorbed thereon. The silver halide emulsion which is mixedwithe such a silver-dye complex has its spectral sensitvity extendedinto the region of absorption of the dye.

To improve further the photographic sensitivities in the visible regionof the spectrum, more effective photographic substrates must be devisedor more direct ways found to detect or respond to the effect that anexposure to light produces in a sensitizing dye.

We have now found in the present invention a method of formingsilver-dye complexes of sensitizing dyes which results in aphotosensitive medium of which the sensitiz- 3,446,619 Patented May 27,1969 ing dye is an integral part, so that energy absorbed by the dye isnot transferred but is used directly to form metallic silver as a resultof the exposure of the silver-dye complex. 7

The silver-dye complexes, which may be highly colored, have the propertyof producing silver directly upon an exposure to light and may bedeveloped by any method of physical development.

One object of this invention is to provide light sensitive silvercomplexes of organic sensitizing dyes. Another object is to providelight-sensitive coatings free from the usual graininess of silver halideemulsions, making possible higher resolving power images. An additionalobject is to provide light sensitive elements which require only verysmall amounts of the light sensitive material. A still further object isto provide a light sensitive system in which no fixation is required ofthe image. Another object is to provide a light sensitive system whichcan be processed using the simple diffusion transfer process foramplifying the initial photo eifect. Another object is to provide lightsensitive layers which need no secondary means of sensitization toproduce visible sensitivity but depend only on the proper choice of dyeto form a light sensitive species of any desired spectral sensitivity.Additional objects will be apparent from the following disclosure.

Our invention involves a reaction product (silver-dye complex) of aspectral sensitizer and silver ion, which product is dispersed in acolloid and coated on a support with any suitable water permeablecolloid binder, preferably gelatin. Following exposure, this lightsensitive coating is physically developed, for example, by contactingwith a conventional photographic emulsion in the presence of a silverhalide developer containing a silver halide solvent and then after ashort time removing the silver halide emulsion in the light to reveal asilver deposit in the areas of exposure in the exposed silver-dyecomplex layer. A positive image will then be obtained in the silverhalide emulsion when it is subsequently exposed, which can be suitablyfixed if desired. It may not be necessary to fix the positive image,depending upon the time of transfer and the amount of silver halidepresent in the silver donor layer. As an alternative developing system,a physical developer solution may be used rather than the diffusiontransfer method of development.

The following dyes are representative merocyanine dyes which may be usedin this process and the region of their spectral response is indicated:

(a) 3-carboxymethyl-5-[ (3-methyl-2-thiazolidinylideneethylidene]rhodanine 420-560 Ill/1.

(b) 5 (3-methyl-2-thiazolidinylidene )ethylidene] rhodanine 460-570 mg(c) 5-['(3-methyl-2-thiazolidinylidene)ethylidene]-2-thio-2,4-oxazolidinedione 400-560 m (d) 3-ethyl-5-[3-methyl-2-thiazolidinylidene ethylidene]-2-thio-2,4-oxazolidinedione430-540 mg.

(e) 1-methyl-5-[ (3 -methyl-2-thiazolidinylidene)ethylidene]-Z-thiobarbituric acid 430-530 III/L (f)3-carboxymethyl-5-[(3-ethyl-2benzoxazolinylidene) ethylidene1rhodanine420-580 m g) 5- 3-ethyl-2-benzoxazolinylidene) rhodanine (h) 5-3-ethyl-2-benzoxazolinylidene) ethylidene] rhodanine 520-560 m,

(i) 3-ethyl-5- (3-ethyl-2-benzoxazolinylidene)ethylidene]l-phenyl-Z-thiohydantoin 520-560 mg (j) 1-carboxymethyl-5-[(3-ethyl-2-benzoxazolinylidene) ethylidene]-3-phenyl-2-thiohydantoin520-560 mm It has been found that a wide variety of dyes includingsensitizing dyes have ability to enter into complexes of varyingstrength with soluble silver salts such as silver nitrate.Representative functional groups which are useful for silver-dyecomplexing ability are Sensitizing dyes with these functional groupsappear to react with silver to form light sensitive species.

These silver-dye complexes are prepared by mixing the dyes with a watersoluble silver salt. The resulting complex can be used in the reactionsolution or colloidal suspension without being isolated. Theoreticallyan equimolar quantity of silver to dye is necessary to form the complex.However, it may be desirable to use an excess of silver depending uponthe particular dye used and the concentration of the dye in solution.

The dyes utilized in the manner of our invention may be water solublebut in the event they are insoluble in water, solutions may be obtainedby dissolving them in suflicient water miscible solvent. The watermiscible solvent is not critical but may be chosen from those which arecompatible with the colloid used as a binder or coating medium.

In the event a solvent soluble silver salt is used, the reaction to formthe complex may be carried out in a suitable solvent.

Various dyes may be used to form the complex including known sensitizingdyes such as cyanines, merocyanines, oxonols, hemicyanines, styryls,hemioxonols, benzylidenes, etc. However, our invention is not limited tothese dyes but includes any dyes which form radiation sensitive silvercomplexes which can be developed by physical development to form avisible image.

The following examples are intended to illustrate our invention but notto limit it in any way.

Example I Under red safelight conditions a light sensitive emulsion wasprepared in the following manner:

To 100 ml. of 5% gelatin were added 4 ml. of a 7 /2 aqueous saponinsolution and 3 ml. of a 10% formaldehyde solution. To 10 ml. of theabove solution were added 0.10 ml. of 0.10 molar silver nitrate solutionand 0.20 ml. of a 1% methanolic solution of the merocyanine sensitizingdye, 3-carboxymethyl-5-(3-methyl-2-thiazolinylidene)ethylidene]rhodanine, maximum 4205 60 mCoatings having a 0.004 inch wet thickness were made on a cellulosetriacetate film support.

After exposure, the coatings were developed by immersing a strip ofunexposed fine grain silver chlorobromide film in a developer having thefollowing composition:

DEVELOPER 1 Methylaminoethanol-SO (18.9% S g 190.0 Hydroquinone g 11.6Dimezone g 1.0 Sodium thiosulfate pentahydrate g 60.0 Potassium iodide g0.42 Water to ml 1000.0 1% methanolic solution of-methyl-3-piperidinylmethyl2-thiooxazolidine ml 20.0

After 4 seconds, the unexposed fine grain silver chlorobromide film wasrolled in contact with the exposed silver-dye layer. After a contacttime of 2 minutes, the two layers were peeled apart in the light toreveal a negative image in the areas of exposure of the exposedsilver-dye layer. The, fine grain silver chlorobromide film 4 was fixedin a solution of sodium thiosulfate, then washed and dried to reveal apositive image.

Example H A light sensitive silver-dye coating was prepared as follows:

In a total of 380 ml. is contained:

10% gelatin solution g 150 7 /2% saponin solution ml 12 10% formaldehydeml l 6 0.1 normal silver nitrate ml 6 Solution containing 1 milligram ofdye per ml. of

solution ml 2.5

E O N H H C=O-C= /C\ \N/ N\ \S I CHzCOOH The merocyanine dye used was:

1-carboxymethyl-5-[ (3 -ethyl-2-benzoxazolinylidene) ethylidene] -3-phenyl-2-thioyhdrantoin.

Coatings having an 0.004 inch wet thickness were made on cellulosetriacetate film support.

After exposure processing was by immersion for 3 minutes in a solutionphysical developed of the following composition.

DEVELOP-ER 2 in dilute potassium hydroxide.

Mix Part A and Part B, 1:1.

The spectral response of this coating as determined by an exposure in awedge spectrograph was from 460-560 m Example HI A light sensitivesilver-dye complex layer was prepared according to the proceduredescribed in Example :11. The exposed coating was processed by immersionin a solution containing in ml. of Water, 0.84 gram of silver nitrateand 1.1 grams of 4,5-(2,3-D fructo pyrano)-2-oxazolidinethione. After animmersion of from 5 seconds to 4 minutes in the silver solution theexposed silVer-type complex layer was immersed for 30 seconds to 3minutes in an undiluted Kodak 1D-l9 solution.

Other complexing agents which formed effective soluble silver salts werethe following:

( 1 3,8-dithiadecane- 1,10-bis-(N-methylpiperidiniump-toluene sulfonate)(2) 7, l 3-dithianonadecane-1,19-bis-(pyridinium-ptoluene sulfonate) (3)3,9-dithiaundecane-1,1l-bis-(N-methylmorpholinium-p-toluene sulfonate)(4) 7,18-diaza-6,19-dioxotetracosane1,24-bis-(pyridinium perchlorate)(5) 3,6,9,12,15,18,21,24-octoxahexa1cosane-1,26-bis- The preferredprocessing solution is one that contains 50.0 g. of compound "(2) and g.of silver nitrate per liter of distilled water. The exposed strip isimmersed in the above solution for seconds, allowed to drain for 10seconds then immersed in D-l9 solution for one minute; a Water rinsestabilizes the processed image.

Although the spectral response of the silver-dye complex coatings isgoverned by the absorption of the silverdye complex, it has been foundpossible to prepare silverdye coatings which are separately sensitive inthe ultraviolet, blue, green and red regions of the spectrum. Byblending the appropriate combinations of silver-dye preparations,panchromatic coatings may be obtained. Since silver dye coatings may bemade which have separate sensitivity to various regions of the spectrum,multilayer color films may be constructed which do not need any filterlayers and which result in very high resolving power in the underlayersbecause of the lack of scattering in the top layers.

Example [IV 4.4 g. of a cyan coupler of the type described in US.

Patent 2,423,730. 385 ml. total volume.

CHzCHzOCHa O This mixture was coated to yield 400 mg. gelatin per squarefoot and 2.6 mg. silver per square foot for the first layer.

(2) The second layer is the same as (1) above ex cept that 2.5 mg. ofgreen sensitizer 3-ethyl-5-(3ethyl-2-benzoxazolinylideneethylidene)-l-phenyl 2 thiohydantoin wassubstituted for the red sensitizer and 5.25 g. of a magenta-formingcoupler of the type described in US. Patent 2,600,788 was substitutedfor the cyan-forming coupler. Coating conditions were identical.

This coated material -was exposed to a multicolored step chart andprocessed in a developer of the following composition:

6 Part B:

(1) Distilled water ml 80.0 (2) Silver nitrate g 5.0

(3) Water to make ml. total volume.

For use add 1 part of B to 9 parts of A.

After 5 minutes development in the above solution, a cyan image wasproduced in the red sensitive layer and a magenta image in the greensensitive layer. Bleaching of the physically developed silver image thatwas also produced in the exposed layers left a 2 color dye imagecontaining a red and green record of the original test object.

Production of color in this 2 layer film could also be produced byplacing the exposed layer in contact with an unexposed layer of a silverbromide emulsion which had been soaked for 30 seconds in a solutioncontaining:

Distilled water ml 750 Sodium sulfite grams 2 2 amino 5diethylaminotoluene monohydrochloride grams 2 Sodium thiocyanate do 10Water to make 1 liter. pH=11.5 with 20% sodium hydroxide.

After a contact time of 2 minutes the two layers were peeled apart toreveal a 2 color image in the exposed 2 layer silver-dye film. Thesilver image in the dye layers may be removed by bleaching to leave onlythe dye image.

Example V A silver-dye complex coating having only an ultravioletsensitivity may be prepared as in Example H except that the dyeCHzCHzOCHn 1 ethyl-15-( 1-ethyl-4(1H)-pyridylidene)-2-thiobarbituricacid is substituted for the dye used in Example II. The spectralsensitivit of this coating was from 378 to 420 m Example VI A silver-dyecomplex coating having only blue-green sensitivity may be prepared as inExample II except the dye COOCHaClIz-N =JJ I 3-ethyl-5-(l-o-sulfobenzoyloxyethyl) -4( 1H) pyridylidene rhodanine is substitutedfor the dye used in Example II. The spectral response of this coatingwas from 420 to 530 my" Example VII A silver-dye complex having onlygreen-red sensitivity may be prepared as in Example II except thecyanine dye 7 aaozac Ha z s zhills aAnhydro-3-ethyl-9-methyl-3'-(3-sulfobutyl) thiacarbocyanine hydroxide issubstituted for the dye used in Example II. The spectral response ofthis coating was from 500 to 630 mu.

Example VIII A silver-dye complex having red and infrared sensitivitymay be prepared as in Example II except the dye O=CN2[(Z-diphenylamino-4-oxo-2-thiazolin-5-ylidene) ethylidene] -3 -ethyl--(3 -ethyl-2-benzoxazolinylidene) ethylidene]-l-phenyl-4-imidazolidone issubstituted for the dye used in Example II. The spectral response ofthis coating was from 500 to 720 III/1..

Example IX A silver-dye complex coating having a panchromatic responsefrom 378 to 630 m may be prepared by blending the silver-dye complexesprepared as in Examples VI, VII and VIII.

The dyes used in Examples I through VI form silver-dye complexes whichhave rather broad absorption bands and correspondingly broad spectralsensitization bands. In some phases of photography it is desirable tohave narrow, sharp spectral sensitization peaks. With silver halideemulsions, this desirable property is brought about by the use of dyeswhich aggregate to give very narrow absorption bands called I bandswhich can confer very narrow, sharp regions of spectral sensitivity onsilver halide emul- SlOIlS.

l C 3H5 Example X A silver-dye complex formed with an aggregatingcyanine dye may be prepared as follows:

(6) A coating having a 0.004 inch wet thickness was made on cellulosetriacetate film support. The spectral sensitivity of this coating showeda sharp peak from 570 to 590 m There are other sensitizing dyes whichform aggregates but do not react directly with silver. It has been foundthat mixing dyes, which do complex with silver ions, with dyes that donot react with silver but do form aggregates results in a lightsensitive coating having the sharp spectral response of the aggregate.

Example XI (1) To ml. of distilled water add 64 grams of 10% gelatin.

(2) Add 5.0 ml. of 7 /2 saponin solution.

(3) Add 2.5 ml. of 10% formaldehyde.

(4) Add 2.5 ml. of 0.1 N silver nitrate.

(5) Dilute total to ml. with distilled water.

(6) To 40 ml. of the above mixture add 0.37 ml. of a solution containing3.5 mg./3-80 ml. of the dye 1,1- diethyl-2,2-cyanine sulfate which formsan aggregate in the gelatin layer.

(7) Add 0.8 ml. of a solution containingl mg./3 ml.

of the merocyanine dye 5[(3-ethyl-2-ot-naphthoxazolinylidene)ethylidene] 3 n heptyl-l-phenyl-Z-thiohydantoin which reacts with silver to form a silver-dye complex. Thespectral response of this coating showed a sharp peak at 565 to 590 me.

Although for most purposes a polymeric binder is used as a vehicle tocoat the silver'dye complex, it has been found possible to sensitizealuminum plates with the silver dye complex in the complete absence ofany binder.

Example X11 (1) A grained aluminum plate was immersed for one minute ina water solution containing 1 mg./ml. of

i HzCOOH CzHs l-carboxymethyl-5-[(3 ethyl 2benzoxazolinylidene)ethylidene]-3-phenyl-2-thiohydantoin (2) The excessdye solution was then rinsed off with distilled water (3) The dyed platewas soaked for one minute in .01 M silver nitrate to form the silver-dyecomplex, then the excess silver was rinsed oif (4) The plate was thendried, exposed to a line image,

and physically developed with the developer of Example II to give asilver image in the areas of exposure Because of the small size and lownumber of nuclei that are created by low levels of exposure to light ofthe silver dye complex, it is desirable that there be as little aspossible of any inhibition or restraining action of physicaldevelopment. Although it is well known that gelatin is an excellentprotective colloid, it was found possible to decrease the protectiveact-ion of the gelatin by adding polymeric compounds which allowed thephysical development to take place at lower levels of exposure than withpure gelatin so that a doubling of the photographic speed results.

9 Example XIII A light sensitive silver-dye complex coating was preparedin a manner identical to that described in Example II, except that fromto 50 ml. of an 8% water solution of copolymer (vinyloxymethyl methylmorpholinium p-toluene sulfonate) '(vinyl acetate) vinyl alcohol JJOCHsPTS' (X, Y, and Z can be whole integers of varying values) was added tothe preparation to be contained in the 380 ml. of total emulsion.

A doubling of the emulsion speed was also obtained in a similar mannerby adding to the gelatin in place of the above copolymer anothercopolymer of vinyl alcoholvinyl N-B-hydroxyethylcarbamoylmethylcarbamate.

[( 1 2 11) x-( H2 H2) 2] ('JONHCHzCONHCHrOHzOH x and z are as above.

Example XIV A light sensitive coating was prepared on a paper supportcontaining 2.6 mg. silver nitrate per square foot, 400 mg. gelatin perspuare foot and 0.065 mg. of the sensitizing dye3-ethyl-5-'(3-e'thyl-2-benzoxazolinylideneethylidene)-1-phenyl-2-thiohydantoin per square foot. The lightsensitive sheet was exposed to a line positive for 2 seconds to a No. 2Photoflood lamp at a distance of 18 inches. After exposure the sheet wascovered with a viscous activator solution of the following composition:

A sheet of a low speed, high resolution silver chlorobromide emulsioncoated to yield a silver coverage of 432 mg. per square foot and gelatincoverage of 320 mg. per square foot was pressed in contact with theviscous solution on the exposed sheet. The sandwich was together for oneminute. Silver was deposited in the exposed areas of the silver-dyelayer :to form a positive print of the line image.

Example XV The light sensitive layer of the preceding example wasprepared and exposed in the manner described. Processing was carried outwith the materials described except that the viscous processing solutionwas contained in a rupturable pod between the two sheets. When thesandwich was drawn between two closely spaced rollers, the viscoussolution was spread evenly between the two layers. Results similar tothose described in the preceding example were obtained.

Example XVI A light sensitive silverdye coating using a benzylidene dyemay be prepared as in Example II except that the dye O=ZI$H on NCH= =s 32 p-dimethylaminobenzylidene rhodanine is substituted for the dye usedin Example H. The spectral sensitivity of this coating was from 460 to590 111,14.

Example XVII A light sensitive silver-dye coating using a styryl dye maybe prepared as in Example 11 except that the dye2-(p-'diethylaminostyryl)-benzothiazole is substituted for the dye usedin Example H. The spectral sensitivity of this coating was from 400 to550 III/4.

Example XVIII A light sensitive silver-dye coating using a hemioxonoldye may be prepared as in Example II except that the dye5-anilinomethylene-3-ethyl-1-phenyl-2 thiohydantoin is substituted forthe dye used in Example II. The spectral sensitivity of this coating wasfrom 460 to 560 mp.

Example XIX A light sensitive silver-dye coating using a thioacetone dyewhich becomes a cyanine dye upon reaction with silver may be prepared asin Example II except that the dyeBis(3-ethyl-2-ot-benzothiazolinylidene)thioacetone is substituted forthe dye used in Example II. The spectral response was from 460 to 580mp.

Example XX Physical development using an electroless copper plating bathmay be used to deposit copper selectively on nuclei produced in animagewise pattern by an exposure to light. When a coating of asilver-dye complex is prepared as in Example 11 and exposed to a KodakModel 60 sensitometer, it may be developed by a ZO-second immersion in acopper physical developer to produce a visible image in the exposedareas which contain 99.7 mg. copper per square foot in the maximumdensity.

By extending the time of development in the copper developer to minutes,high neutral density images of 1.40 are obtained. Copper analyses ofsensitometric strips indicate that over mg. of copper per square footexists in the image area. i

The composition of the electroless copper plating bath used to depositcopper only on the photoproduced silver specks was Cupric nitrate grams50 Other silver compounds which may be used to form the silver-dyecomplex include water soluble silver salts such as silver acetate,silver benzoate, silver citrate, silver fluoride, silver lactate, silverlaurate, silver p-toluenesulfonate, and the like. Since these are merelyrepresentative soluble silver salt compounds, it will be apparent to oneskilled in the art that other soluble silver compounds may also be usedwithin the scope of our invention.

When diffusion transfer physical development is employed, any of theknown silver halide emulsions may be used in contact with the lightsensitive, exposed, silver-dye complex emulsion, such as silverchlorobromide, silver chloroiodide, silver chlorobromoiodide, silverbromide, and silver bromoiodide.

The binder for the light sensitive silver-dye complex is not criticalbut may be any water permeable material such as the colloids known foruse in silver halid photography including gelatin,carboxymethylcellulose, zein, various synthetic resins such as polyvinylalcohol, acrylic resins, etc., collodion, albumin, cellulosederivatives, and the like.

Light sensitive silver-dye layers may also be made in the completeabsence of a binder by coating a grained aluminum support with asolution containing a mixture of the silver-dye complex.

In preparing the light sensitive elements using a binder, the silver-dyecomplex is dispersed in a suitable binder and then the mixture is coatedon a support using any of the known coating methods. Supportingmaterials can be any of the known materials for this purpose, such asfilm base (e.g., cellulose nitrate film, cellulose ester film, etc.),plastic supports (e.g., polyethylene, polyethylene terephthalate, etc.),paper, metal, glass, and the like.

The wet thickness of the coatings can be in the range from about 0.001to about 0.01 inch with a preferred wet thickness in the range fromabout 0.003 to about 0.006 inch. Thicker coatings can also be employedwithout detracting from the invention.

Although the concentrations of the various components of the lightsensitive composition of the invention can vary over a wide range, ithas been found that quite useful coating compositions are preparedwherein the binder is present in the range up to about by Weight of thetotal coating melt and wherein the silver-dye complex is present in therange of from about .1% to about 10% by weight of the total coatingmelt.

Although the normal methods of physical development can be used,including swabbing with an aqueous silver solution such as a dilutesilver nitrate solution and then immersing the swabbed layer in aphotographic silver halide developing solution, followed by washing thede veloped print with water to stabilize it, other methods fordevelopment of the exposed layers of the invention compriseincorporating in the said layers a silver complex or salt, such assilver-thiosulfate complex or the silver salt of4,5-(2,3-D-fructopyrano)-2 oxazolidinethione, and the like. In processeswhere silver plus a complexing agent is incorporated in the sensitivelayer, such layers are normally developed by treatment with aconventional silver halide developing solution.

The light sensitive layer of this invention when normally exposed to apositive image, results in a negative image. However, a reversal systemcan be employed wherein a positive image will be obtained. Afterexposure of the light sensitive coating, followed by a mild physicaldevelopment, a mild bleach is used to remove the developed silver. Byflashing to light or by similar fogging action followed by physicaldevelopment, a positive image is obtained.

In the above examples, the images formed by physical development aresilver. However, other metals are known for use in physical developmentand can be used for the same purposes as silver by the appropriatesubstitution of metallic salts. Metals which are members of theelectromotive scale below hydrogen are those which are most commonlyemployed for this purpose and include copper,

mercury, platinum, gold, silver, and the like. The use of these metalsto form images according to our invention using solutions known aselectroless plating baths is within the scope thereof.

At the instant of exposure the coated silver-dye emulsion is essentiallygrainless, since no particulate matter may be observed at the highestmagnification available with the electron-microscope.

Since the light sensitive species is essentially of molecular size, theresolving power of these coatings is exceptionally high. No upper limithas been placed on the resolving power, but 800 lines per millimeterhave been measured on a sample prepared according to Example I. Anotherunusual property that results from the physical development of thesesilver-dye coatings is the extremely high acutance which is greater thanany silver halide material. Microdensitometer edge traces of sharplyexposed lines yield results which indicate the physically developedsilver dye materials have infinite acutance thus yielding photographicquality unobtainable with any other recording medium.

By radiation as used herein is intended visible light, infrared andultraviolet, as well as X-rays, gamma rays, etc.

It will be appreciated that the light sensitive silver-dye complex canbe prepared to be sensitive to a particular wavelength or wavelengthband. However, these light sensitive silver-dye complexes may be furthersensitized by having sensitizing dyes added thereto.

It will also be appreciated that the silver-dye complexes of ourinvention can be used in color processes with a para phenylenediaminetype of silver halide developer whose oxidation products can couple withdye forming couplers as is used in conventional color photography. Thedye forming coupler or couplers can be incorporated in the emulsion inone or more layers or may be present in the developing solution. Any ofthose known in the art for use in color photography may be used in ourinvention.

In a particular embodiment of our invention, a dye which is used as aprecursor to release para phenylenediamine type silver halide developersmay be used to form the silver-dye complex. In this situation, the dyecleaves under alkaline conditions to release the para phenylenediaminetype silver halide developer. This developer then develops the exposedsilver complex in conjunction with the soluble metal salt in thephysical developer solution and forms an oxidized para phenylenediamineproduct which is capable of coupling with a dye forming couplerimagewise. By using a dye which is capable of cleaving as above, to formthe silver-dye complex, it is possible to incorporate a paraphenylenediamine developer as a precursor and the light sensitivecoating.

When the light sensitive silver-dye complexes of this invention are usedin one or more layers to form a color product, it is necessary to removethe silver image to obtain the dye image. This can be accomplished bynormal bleaching operations which are used according to conventionalcolor processes. Reversal may also be accomplished by conventionalmeans, by developing the exposed image and bleaching, after which theremaining silver complex is exposed to a flash exposure and redeveloped.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention as described hereinabove and as defined in the appendedclaims.

We claim:

1. A photographic emulsion comprising a radiationsensitive materialconsisting essentially of a reaction product of silver ion with aspectral sensitizing dye selected from the class consisting of cyanines,merocyanines, oxonols, hemicyanines, hemioxonols, styrls andbenzylidenes which reaction product, upon exposure to radiation, formsan active site for physical development.

2. A photographic emulsion of claim 1 in which said dye is a cyanine.

3. A photographic emulsion of claim 1 in which said dye is amerocyanine.

4. A photographic emulsion of claim 1 in which said dye is an oxonol.

5. A photographic emulsion of claim 1 in which said dye is ahemicyanine.

6. A photographic emulsion of cclaim 1 in which said dye is ahemioxonol.

7. A photographic emulsion of claim 1 in which said dye is a styryl.

8. A photographic emulsion of claim 1 in which said dye is abenzylidene.

9. A photographic emulsion of claim 1 in which said dye is a2-thiohydantoin spectral sensitizing dye.

10. A photographic emulsion of claim 1 in which said dye isl-carboxymethyl--[(3-ethyl 2benzoxazolinylidene)ethylidene]-3-phenyl-2-thiohydanion.

11. A photographic emulsion of claim 1 in which said dye is5-[(3-ethyl-2-u-naphthoxazolinylidene)ethy1idene]-3-n-heptyl-l-phenyl-Z-thiohydantoin.

12. A photographic emulsion of claim 1 in which said dye is1-carbethoxy-5-[(3-ethyl-2-benzoxazolinylidene)-ethylidene]-3-phenyl-2-thiohydantoin.

13. A photographic element comprising a support having thereon at leastone radiation-sensitive layer in which the radiation-sensitive materialconsists essentially of a reaction product of silver ion with a spectralsensitizing dye selected from the class consisting of cyanines,merocyanines, oxonols, hemicyanines, hemioxonols, styryls andbenzylidenes, which reaction product, upon exposure to radiation,becomes an active site for physical development.

14. A photographic element of claim 13 in which said dye is a cyanine.

15. A photographic element of claim 13 in which said dye is amerocyanine.

16. A photographic element of claim 13 in which said dye is an oxonol.

17. A photographic element of claim 13 in which said dye is ahemicyanine.

18. A photographic element of claim 13 in which said dye is ahemioxonol.

19. A photographic element of claim 13 in which said dye is a styryl.

20. A photographic element of claim 13 in which said dye is abenzylidene.

21. A photographic element of claim 13 comprising a support havingthereon at least one radiation-sensitive layer comprising a waterpermeable colloid containing said radiation-sensitive material.

22. A photographic element of claim 13 in which said layer has spectralsensitivity only in the region of absorption by said reaction product.

23. A photographic element of claim 13 in which said dye is a2-thiohydantoin spectral sensitizing dye.

24. A photographic element of claim 13 in which said dye is1-carboxymethyl-5-[(3-ethyl-2-benzoxazolinylidene)-ethylidene]-3-phenyl-2-thiohydantoin.

25. A photographic element of claim 13 in which said dye is5-[(3-ethyl-2-a-naphthoxazolinylidene)ethylidene]-3-n-heptyl-1-phenyl-2-thiohydantoin.

26. A photographic element of claim 13 in which said dye is l-carbethoxy5 [(3-ethyl-2-benzoxazolinylidene) ethylidene]-3-phenyl-2-thiohydantoin.

27. A process for forming a metallic image in an exposedradiation-sensitive layer in which the radiationsensitive materialconsists essentially of at least one radiation-sensitive reactionproduct of silver ion with a spectral sensitizing dye selected from theclass consisting of cyanines, merocyanines, oxonols, hemicyanines,hemioxonols, styryls and benzylidenes, comprising contacting said layerwith a solution of a metallic compound and a reducing agent.

28. A process of claim 27 in which said radiationsensitive material isdispersed in a water permeable colloid.

29. A photographic process of claim 27 in which said dye is a cyanine.

30. A photographic process of claim 27 in which said dye is amerocyanine.

31. A photographic process of claim 27 in which said dye is an oxonol.

32. A photographic process of claim 27 in which said dye is ahemicyanine.

33. A photographic process of claim 27 in which said dye is ahemioxonol.

34. A photographic process of claim 27 in which said dye is a styryl.

35. A photographic process of claim 27 in which said dye is abenzylidene.

36. A process for forming a metallic image in an exposedradiation-sensitive layer in which the radiationsensitive materialconsists essentially of at least ,one radiation-sensitive reactionproduct of silver ion with a spectral sensitizing dye selected from theclass consisting of cyanines, merocyanines, oxonols, hemicyanines,hemioxonols, styrls and benzylidenes, comprising contacting said layerwith a silver halide emulsion in the presence of a silver halidedeveloping agent and a silver halide solvent.

37. A process of claim 36 in which said radiation-sensitive material isdispersed in a water permeable colloid.

38. A process for forming a silver image in an exposed light sensitivelayer in which the light sensitive material consists essentially of atleast one light sensitive reaction product of silver ion with a spectralsensitizing dye selected from the class consisting of cyanines,merocyanines, oxonols, hemicyanines, hemioxonols, styryls andbenzylidenes, dispersed in a water permeable colloid, comprisingcontacting said layer with a solution of a silver compound and areducing agent to form a silver image, bleaching the silver image,exposing to light and developmg.

39. A process for forming a color dye image in an exposed lightsensitive layer in which the light sensitive material consistsessentially of at least one light sensitive reaction product of silverion with a spectral sensitizing dye selected from the class consistingof cyanines, merocyanines, oxonols, hemicyanines, hemioxonols, styrylsand benylidenes, comprising contacting said layer with a solution of ametallic compound and a primary amino aromatic silver halide developerin the presence of a dye forming coupler, capable of forming a dye bycoupling to the oxidation product of said developer and bleaching thesilver image.

40. A process for forming a color dye image in an exposed lightsensitive layer in which the light sensitive material consistsessentially of at least one light sensitive reaction product of silverion with a spectral sensitizing dye selected from the class consistingof cyanines, merocyanines, oxonols, hemicyanines, hemioxonols, styrylsand benzylidenes, and a color forming coupler, comprising contactingsaid layer with a solution of a metallic compound and a reducing agentwhose oxidized form does not couple with the coupler to form a dye,bleaching the metallic image formed, exposing and developing with aprimary amino aromatic silver halide developer containing a silvercompound and bleaching the silver image.

References Cited UNITED STATES PATENTS 2,735,766 2/1956 Hill 961032,993,393 7/1961 Hunt 96-102 3,206,309 9/1965 Haist 9694 (Otherreferences on following page) 15 16 FOREIGN PATENTS Chemical Abstracts,Vol 40, 9926i, 9927a (1956). 733,731 7/1950 Gr tB 't Leukoev aqd S.Watanson, (Kine-Photo Inst, Mos- 524 500 8/1940 gg g jgg cow(Zhur.F1z.Kh1m. 30, 161-71 (1956). K. I. Pokrovskaya 1.1.).

OTHER REFERENCES Natunson, 1., Phys. Chem. U.S.S.R., vol. 14, pp. 989- 5TRAVIS BROWN Examine- 995, 1940. M. F. KELLEY, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,446,619 May 27 1969 Paul B. Gilman et a1 It is certified that error appearsin the above identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1 line 50 "by a mobile silver io nfrom the silver halide latticeto" should read by the dye is transferred to the silver halide in such aline 63, "withe" should read with Column 2, line '70 insert (k)l-carbethoxy-S- [(S-ethyl-2-benzoxazolinylidene) -ethylidene]3pheny1-2-thiohyndantoin, 520-560 m Column 4, line 24, "thioyhdrantoin"should read thiohydantoin line 29, "developed" should read developerline 62, "silver-type" should read silver-dye Columns 5 and 6, lines 40to 52 the formula should appear as shown below:

H CH OCH CH CH OCH Column 12 line 75 "styrls" should read styryls Column13, line 10 "cclaim" should read claim line 20 "thiohydanion" shouldread fthiohydantoin Column 14 line 26 "styrls" should read styrylsSigned and sealed this 9th day of June 1970.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents

